Apparatus and method for testing the runnability of corrugating medium

ABSTRACT

Apparatus and method for testing the runnability of corrugating medium in the manufacture of corrugated paperboad involving fluting an elongated strip of the medium as it is fed between a pair of coacting corrugating rolls rotating at constant speed. As the medium is passed between the rolls, the stress-strain on the medium is progressively increased and the medium is subjected to increasing stress-strain until a critical level is reached.

United States Patent 1 McKee I [111 3,776,029 [4 1 Dec. 4, 1973 4] APPARATUS AND METHOD FOR TESTING THE RUNNABILITY OF CORRUGATING MEDIUM [75] Inventor: Robert C. McKee, Appleton, Wis.

[73] Assignee: The Institute of Paper Chemistry, Appleton, Wis.

[22] Filed: Dec. 10, 1971 [21] Appl. No.: 206,672

[52] US. Cl. 73/88 R, 156/64, 156/205, 156/462, 156/379 [51] Int. Cl. G01b 5/30 [58] Field of Search 156/64, 205, 206, 156/207, 462, 470, 378; 73/955, 88, 89

[56] References Cited UNITED STATES PATENTS 3/1964 Early 156/64 3,676,247 7/1972 Morris et al. 156/205 Primary ExaminerAlfred L. Leavitt Assistant ExaminerFrank Frisenda Attorney-William B. Anderson et a].

571 ABSTRACT Apparatus and method for testing the runnability of corrugating medium in the manufacture of corrugated paperboad involving fluting an elongated strip of the medium as it is fed between a pair of coacting corrugating rolls rotating at constant speed. As the medium is passed between the rolls, the stress-strain on the medium is progressively increased and the medium is subjected to increasing stress-strain until a critical level is reached.

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APPARATUS AND METHOD FOR TESTING TI-IE RUNNABILITY OF CORRUGATING MEDIUM The present invention relates to corrugated paperboard evaluation and, more particularly, to an apparatus and method for testing the runnability of corrugating medium in the manufacture of corrugatedpaperboard.

The manufacturing of corrugated paperboard from which ocrrugated boxes are formed is typically a twostep operation: first, the corrugating medium and the liners or facings are produced, and, second, the liners and medium are fabricated or combined into corrugated paperboard. A most important quality of corrugating medium is runnability, i.e., the ability of the medium to withstand stresses and strains caused in the corrugating process. The higher the corrugating speed,

the more severe are the stresses and strains imposed on the corrugating medium. Each medium has a critical speed for given conditions above which it cannot be corrugated without impairing the medium.

Preferably, the runnability of the corrugating medium should be evalued at the time the medium is produced rather than at the time of fabrication of the medium into corrugated paperboard. As the manufacture of the corrugated paperboard may not occur for an extended period of time after the corrugating medium is produced and such manufacture will frequently occur away from the paper mill in a converting or corrugating plant, it is more efiicient and economic to test the corrugating medium at the time of production. In fact, it is desirable to know the potential runnability of the medium at the time it is produced on the paper machine because a number of days or even weeks may pass be fore the board is run on a corrugator which is the only practical means currently availabe for determining the runnability. During this period many hundreds of tons of corrugating medium will have been produced'of unknown runnability. In any event, it is most desirable to check the runnability prior to corrugating the medium for effective machine operation.

In determining most characteristics of the medium, a number of well known test procedures may be employed which are standard in the paper induttry. However, no test or procedure has been satisfactorily predictive for evaluating runnability of corrugating medium. As corrugating is presently being conducted at increased speeds, it is desirable to evaluate the runnability characteristic of the corrguating medium prior to its conversion on a corrugating machine particularly since there is no way of changing the runnability once the medium has been made up into rolls.

Accordingly, an object of the present invention is to provide an apparatus and method for testing the runnability of corrugating medium off a paper machine so as to avoid the production of many hundred tons of medium of substandard runnability. I

Another object of the invention is to provide an apparatus and method for rapidly and effectively evaluating the runnability characteristics of corrugating medium prior to corrugation of the medium.

These and other objects of the present invention will become apparent with reference tothe following de-. tailed description and accompanying drawing, in which: i

FIG. 1 is a plan view of the apparatus of the invention useful in the present method for determining the runnability of corrugating medium;

FIG. 2 is a side elevational view of the apparatus shown in FIG. 1; and

FIG. 3 is a partial cross-sectional view taken along.

the line 33 in FIG. 2.

Briefly, with reference to thedrawing s, there can be seen apparatus generally designated by the reference numeral for testing the runnability of corrugating medium prior to corrugation. The apparatus. 10 generally comprises a holder 12 mounted :for rotation for providing an elongated strip or specimen 14 of the medium to be tested; a pair of cooperating or interacting corrugating rolls l6 and 18 for receiving the specimen 14 from the holder 12 and for corrugating the specimen as it passes therebetween by forming flutes; a drive means 20 for rotating the corrugating rolls l6 and 18 at a constant speed; and a tension applying means 22 responsive to the passage of the medium between the rolls 16 and 18for progressively increasing the tension applied by the holder 12. Driving the rolls l6 and 18 at a constant speed while progressively increasing the tension applied by the holder 12 subjects the medium to progessive increases in tension until the critical level of runnability of the medium is reached.

More particuarly', the holder 12 for containing the elongated specimen 14 of the medium includes a spool 24 which is adapted to rotate in both clockwise and counter clockwise directions and which is generally cylindrical in shape (FIGS. 1 and 2). The spool 24 has a slot 26 therein extending transversely of its periphery. The specimen 14 is wound upon the spool 24by engaging one end within the slot 26 and then rotating the spool in a clockwise direction. The spool 24 is mounted upon a vertically extending shaft 28 joumalled for rotation in an upper plate 30 so that the spool is rotatable in a horizontal plane.

For purposes of holding the specimen 14 on the spool 24, a holding means 31 is provided. The holding means 31 serves to nold the specimen in wound condition on the spool 24 of the holder 12 prior to testing in the corrugating rolls 16 and 18. As the specimen 14 is unwound from the holder 12 upon counter clockwise rotation of the spool 24, it passes in front of a lamp 34 coacting with the photocell 32 causing the light from the lamp to be blocked from reaching the photocell. The photocell is electrically connected to a solenoid 38, the armature 40 of which has a pressure bar 42 at the end thereof which engages the specimen 14 on thespool 24' to maintain it on the spool 24 without uncoiling until the leading end of the specimen passes under the photocell 32. When the specimen passes under the photocell, the solenoid 38 releases the pressure bar 42 and disposed in parallel to each other and to the roll for corrugating the medium. One of the corrugating rolls, typically the roll 16, has a fixed axis of rotation on a drive shaft 46, while the other of the corrugating rolls,

typically the roll 18, has a translatable shaft 47 and is driven through meshing action of the teeth 45 when the corrugating roll 18 is pressed against the roll 16. Thus, the roll 16 is a fixed roll and the roll 18 can be considered a pressure roll.

Pressure applying means 48 is provided for the corrugating roll 18 and comprises the photocell 32 previously described which actuates a ram 49 through a mechanical-electrical arrangement (not shown). The

ram 49 actuates a bell crank 50 by forcing one arm 50a. The other arm 50b pivots on a shaft 50c. The elbow 50d of the bell crank is connected to the shaft 47 of the corrugating roll 18. Thus, the pressure applying means 48 is actuated when the specimen enters the nip and avoids unnecessary wear on the corrugating rolls.

A stop 52 is disposed on the frame of the apparatus in position to engage the crank arm 500.

Thus, the ram 49 of the pressure applying means 48 rotates the bell crank 50 aboutthe shaft 50c causing the shaft for the corrugating roll 18 to apply pressure to the roll against the fixed corrugating roll 16. When the pressure is released, the stop 52 limits the movement of the bell crank 50 and opening of the nip 44 between the corrugating rolls 16 and 18.

The corrugating rolls 16 and 18 are heated by being supported upon a plate 54, which is heated by suitable means to a temperature of about 350F. Heating the corrugating rolls 16 and 18, and hence the specimen, provides for better evaluation of the specimen.

The drive means for the corrugating rolls l6 and 18 can best be seen in FIG. 2. The drive means 20 rotates the corrugating rolls at a constant speed and comprises a drive motor 56 for operating a gear reducer 58 which through suitable gearing turns a horizontally disposed gear 60. The gear 60 is on the shaft 46 of the corrugating roll 16 and consequently causes rotation thereof. As aforesaid, the corrugating roll 18 is driven by the meshing action of its teeth 45 with the teeth of the roll 16 and is not separately driven. It should be apparent, however, that the rolls l6 and 18 could be separately driven.

After passing between the fixed corrugating roll 16 and the pressure roll 18, the specimen 14 which has been corrugated by the rolls emerges from the nip 44 and contacts a guide 62 which directs the corrugated specimen to an actuating arm 63 of a microswitch 64.

. The arm 63 actuates the switch 64 upon passage of the corrugated medium between the corrugating rolls 16 and 18.

The tension applying means 22 is actuated upon the passage of the specimen 14 between the corrugating rolls l6 and 18 for progressively increasing tension by braking of the spool 24 and is particularly illustrated in FIGS. 2 and 3. The tension applying means 22 is actuated by the microswitch 64 positioned near the rolls 16 and 18. The tension applying means 22 includes a cam 68 mounted for rotation in a vertical plane, the cam being generally elliptical in shape. The cam 68 is mounted upon a drive shaft 69, actuated by a motor 70. The motor 70 is actuated by the microswitch 64 upon the passage of the corrugated specimen between the rolls. Rotation of the cam 68 by the drive shaft 69 causes, through linkage means 76, the tightening of a flexible tape or belt 78 about the periphery of a brake cylinder 80. The flexible tape 78 is wrapped preferably at least 450 about the cylinder 80 to provide sufficient engagement and is connected to the linkage means 76 and to fixed points 82 on the frame of the apparatus 10.- Preferably, a pair of flexible tapes 78 formed of steel or the like are operatively connected to the linkage 76, wrapped about the cylinder and attached at their other ends to fixed points 82. Upon rotation of the cam 68 by the drive shaft 69 connected to the motor 70, the flexible tapes 78 are tightened about the cylinder 80 and the spool is braked, thereby increasing tension on the specimen between the spool 24 and the corrugating nip 44. A magnetic braking system or other braking system could also be employed, although the abovedescribed system is presently preferred.

The linkage means 76 for connecting the cam 68 to the flexible tapes 78 includes a pivot arm 84 having a cam follower 86 mounted at the lower end thereof. Rotation of the cam 68 results in movement of the pivot arm 84 about a fixed point 88 at the upper end thereof as the cam follower 86 is engaged by the face of the cam 68. The arm 84 connects to a spring 90 which connects to a lug 92. The free lug is fixed to the ends of the tapes 78. The tension in the spring 90 is adjustable so that the amount of tension on the tapes 78 can be set to give tension build up in the specimen. Thus, the tension applied by the spring 90 to the tapes 78 places a frictional braking force on the cylinder 80 which resists the rotation thereof resulting from the specimen being pulled from the spool 24 by the pulling force of the corrugating rolls l6 and 18. As the braking increases on the cylinder 80, and as the cam 68 continues to rotate, a corresponding increase in tension occurs in the specimen 14 between the spool 24 and the corrugating nip 44.

Also connected to the drive shaft 69 of the motor 70 is an actuator 94. This actuator 94 rotates together with the cam 68. At the completion of one full revolution of the cam 68, the actuator 94 is in position to trip a switch 96 adjacent thereto which stops the motor 70 and also stops rotation of the cam 68. If the microswitch 64 is still held in an actuated position by the passage of the specimen 14, the action of the switch 96 will be overridden and the motor 70 will continue to rotate the cam 68 until the microswitch 64 is released.

The length of the specimen 14 being tested can be adjusted so that before release of the microswitch 64, the tail of the specimen 14 passes between the corrugating nip 44, thereby uncovering the photocell 32 and exposing it to light from the lamp 34. Activation of the photocell 32 releases the pressure bar 42 and the pressure applied by the ram 49 maintaining the pressure roll 18 in coacting relationship with the fixed roll 16. This opens the corrugating nip 44.

The specimen holder 12 and the tension applying means 22 in the illustrated embodiment are mounted upon a plate 100 suspended from the upper plate 30 by a plurality of lock bolts 102 and flexure plates 104 (FIG. 2). When the lock bolts 102 are removed, the

tension applying means 22 and the suspended plate 100 are connected to the upper plate 30 only by the flxure plates 104. Attached at the location of one of the flexure plates 104 is a strain-gauged load cell mounted to detect movement of plate 100 relative to plate 30. The

load cell is connected to a suitable power supply, am-

is in an unloading cycle. This allows calibration of the apparatus so that the exact tension applied to the corrugating medium at progressive intervals during the testing cycle can be determined. When the apparatus is not being used in calibration, the load cell preloaded springs are released and the lock bolts 102 are secured in position to attach the suspended plate 100 to the upper plate 30.

After the specimen 14 has been corrugated by the rolls l6 and 18, the runnability index can be determined using an illuminated, transparent testing rack 106 (FIG. 1 The fluted specimen is placed in registration with solid flutes 108 formed in the rack 106. Comparison of the specimen with this fluted standard permits determination of the runnability indx of the medium. While the specimen is disposed on the testing rack 106, any fractures therein are noted and the number of good flutes occurring before any fracturing of the specimen is also noted. In use of the testing rack 106, the first flutes in the specimen are discounted as they are formed bfore tension has been applied by the tension applying system 22 to the specimen. This section of the specimen is referred to as the leader. The remaining flutes beginning with the first flute after the leader are counted and used as the runnability index. The number of flutes formed before initiation of fracturing of the specimen can be related to the tension on the specimen as the rotational speed of the corrugating rolls 16 and 18 is constant and the braking force applied to the cylinder 80 (and hence the specimen holder 12) increases proportionally with time. Therefore, runnability is measured in terms of specimen tensions, and the runnability index is the number of flutes formed before occurrence of fracturing of the specimen.

In use of the present apparatus 10, the specimen 14 to be tested is wound clockwise upon the spool 24 of the specimen-holder 12. The specimen leading end is manually inserted into the corrugating nip 44 between the fixed and pressure rolls 16 and 18, respectively. Placing the specimen in front of the photocell 32 while feeding it into the nip causes the pressure bar 42 to be released from the coiled specimen upon the holder so that the specimen can uncoil freely. Moreover, the

pressure roll 18 is caused to move into coacting relationship with the fixed roll 16. The motor 56 is actuated and as the specimen 14 passes through the corrugating nip 44, it engages the microswitch actuating arm 63 which trips the switch 64 and signals the motor 70 of the tension applying system 22 to rotate the cam 68. Rotation of the cam 68 causes the flexible tapes 78 to apply progressively increasing tension upon the brake on a particular machine or in a predetermined -opera- 6 tion. Knowing the critical tension for the particular medium allows selection of the proper medium for the use desired and the corrugating apparatus available.

In an alternative manner of practicing the method of the present invention, the medium specimen is uncoiled at constant tension and is fluted at progressively increasing speed until a critical level of speed is reached at which flutes fracture. In this method, the corrugating rolls are accelerated at a known and adjustable rate and the specimen holder is rotatedat like speed. Thus, the web tension at the speed is held substantially constant. The fluted specimen is then compared against the fluted standard to determine the runnability index.

Thus, there is provided an apparatus and method for testing the runnability of corrugating medium. The apparatus and method of the invention are efficient in testing the runnability of corrugating medium utilized in the manufacture of paperboard as soon as it is made and right off the paperboard machine or prior to conversion on a corrugator in the manufacture of corrudium is subjected to increases in stress and strain until a critical level of runnability of the medium is reached at which flutes fracture, whereby the runnability of the medium may be determined from the number of flutes formed before initiation of fracturing.

2. A method according to claim 1, further comprising heating the medium as it is fluted.

3. A method according to claim 1 wherein fluting is effected at constant speed and the feeding is effected under conditions of progressively increasing tension on the strip of the medium.

4. A method according to claim 1, further comprising determining the distance traveled during said increasing of the stress-strain build up before fracture of the fluted medium.

'5. A method of testing the runnability of corrugating medium, comprising the steps of coiling an elongated strip of the medium, uncoiling the medium at constant tension, and fluting the medium at progressively increasing speed as it is uncoiled :at constant tension, whereby the medium is subjected to increasing stressstrain build up until the critical level of runnability of 'the medium is reached at which flutes fracture. 6. An apparatus for testing the runnability of a specimen of corrugating medium to'determine the critical level of runnability of the medium comprising, in combination,

specimen holding means for holding and feeding an elongated test specimen strip of the medium from of the specimen to the tail end from the leading end to the end of the specimen a as it passes therebetween, each of said corrugating 'rolls comprising a wheel having a plurality of teeth spaced about the periphery thereof,

drive means for rotating said coacting corrugating rolls at a constant speed, and

means actuated upon passage of the lead end of a test specimen through said corrugating rolls, for applying a testing cycle of progressively increasing tension to the test specimen passing from said specimen holding and feeding means to said corrugating rolls, such that fracturing of the corrugation flutes formed in the test specimen results during the progressive tension increase provided by said tension applying means, whereby the runnability of corrugating medium may be determined from the number of unfractured flutes formed in the test specimen by said apparatus subsequent to the application of the progressively increasing tension by said tension applying means.

7. An apparatus in accordance with claim 6 wherein one of said corrugating rolls has a fixed axis of rotation and the other of said corrugating rolls has a movable axis of rotation whereby said rolls may be moved apart and together, and further including means for compressing said corrugating rolls together, said compressing means being actuated upon feeding of the leading end of a test specimen to said corrugating rolls.

8. An apparatus in accordance with claim 6 wherein said holding and feeding means'comprises a rotatably mounted spool for holding and feeding the specimen to said rolls and wherein said tension applying means comprises a brake cyliinder in connection with said ro tatable spool, at least one braking belt wrapped about said brake cylinder, and motor and linkage means for causing the progressive tightening of said braking belt about the periphery of said brake cylinder, and means for actuating said feed motor upon passage of the lead end of the specimen through said corrugating rolls.

9. An apparatus in accordance with claim 6 further including means for measuring the tension on a specimen passing from said holding and feeding means to said corrugating rolls during actuation of said tension applying means.

10. An apparatus in accordance with claim 9 wherein said holding and feeding means is releasibly mounted to be movably responsive to said tension and wherein said tension detecting means comprises a strain-gauged load cell mounted to detect such relative responsive movement.

11. An apparatus in accordance with claim 6 further comprising fluted means for examining the corrugating medium after its passage between said rolls to determine the runnability index. 

1. A method of testing the runnability of corrugating medium, comprising the steps of feeding an elongated strip of the medium, fluting the medium, increasing the stress-strain build up on the medium, such that the medium is subjected to increases in stress and strain until a critical level of runnability of the medium is reached at which flutes fracture, whereby the runnability of the medium may be determined from the number of flutes formed before initiation of fracturing.
 2. A method according to claim 1, further comprising heating the medium as it is fluted.
 3. A method according to claim 1 wherein fluting is effected at constant speed and the feeding is effected under conditions of progressively increasing tension on the strip of the medium.
 4. A method according to claim 1, further comprising determining the distance traveled during said increasing of the stress-strain build up before fracture of the fluted medium.
 5. A method of testing the runnability of corrugating medium, comprising the steps of coiling an elongated strip of the medium, uncoiling the medium at constant tension, and fluting the medium at progressively increasing speed as it is uncoiled at constant tension, whereby the medium is subjected to increasing stress-strain build up until the critical level of runnability of the medium is reached at which flutes fracture.
 6. An apparatus for testing the runnability of a specimen of corrugating medium to determine the critical level of runnability of the medium comprising, in combination, specimen holding means for holding and feeding an elongated test specimen strip of the medium from the leading end of the specimen to the tail end thereof, a pair of coacting corrugating rolls having a corrugating nip for receiving the test specimen from said holding and feeding means and for corrugating the specimen to form corrugation flutes progressively from the leading end to the tail end of the specimen as it passes therebetween, each of said corrugating rolls comprising a wheel having a plurality of teeth spaced about the periphery thereof, drive means for rotating said coacting corrugating rolls at a constant speed, and means actuated upon passage of the lead end of a test specimen through said corrugating rolls, for applying a testing cycle of progressively increasing tension to the test specimen passing from said specimen holding and feeding means to said corrugating rolls, such that fracturing of the corrugation flutes formed in the test specimen results during the progressive tension increase provided by said tension applying means, whereby the runnability of corrugating medium may be determined from the number of unfractured flutes formed in the test specimen by said apparatus subsequent to the application of the progressively increasing tension by said tension applying means.
 7. An apparatus in accordance with claim 6 wherein one of said corrugating rolls has a fixed axis of rotation and the other of said corrugating rolls has a movable axis of rotation whereby said rolls may be moved apart and together, and further including means for compressing said corrugating rolls together, said compressing means being actuated upon feeding of the leading end of a test specimen to said corrugating rolls.
 8. An apparatus in accordance with claim 6 wherein said holding and feeding means comprises a rotatably mounted spool for holding and feeding the specimen to said rolls and wherein said tension applying means comprises a brake cyliinder in connection with said rotatable spool, at least one braking belt wrapped about said brake cylinder, and motor and linkage means for causing the progressive tightening of said braking belt about the periphery of said brake cylinder, and means for actuating said feed motor upon passage of the lead end of the specimen through said corrugating rolls.
 9. An apparatus in accordance with claim 6 further including means for measuring the tension on a specimen passing from said holding and feeding means to said corrugating rolls during actuation of said tension applying means.
 10. An apparatus in accordance with claim 9 wherein said holding and feeding means is releasibly mounted to be movably responsive to said tension and wherein said tension detecting means comprises a strain-gauged load cell mounted to detect such relative responsive movement.
 11. An apparatus in accordance with claim 6 further comprising fluted means for examining the corrugating medium after its passage between said rolls to determine the runnability index. 